This invention relates to a vibration detector and more particularly to an enclosed device having a light-change detector and a light source that is modulated in response to mechanical vibration of the enclosure, and which enclosed device is suitable for use as an intrusion alarm.
An intrusion alarm system is described in my U.S. patent application Ser. No. 878,045, filed Feb. 15, 1978, which includes an integrated circuit photo-sensing chip that produces an alarm when the light being sensed is altered by a person, possibly an unwelcome intruder, moving about in the vicinity of the sensor. The alarm will be triggered on, either by an increase in the intensity of the sensed light as a result of its intensification by reflection from the person's light-colored clothing or by a decrease in the intensity of the sensed light as a result of the person having moved between the source of light and the sensor.
It is an object of the present invention to provide a vibration detector which produces an alarm signal when subjected to mechanical vibration exceeding a predetermined amplitude.
It is a further object of this invention to provide a vibration detector suitable for mounting on a door or a window for sounding an alarm when illicit entry through the window or door is attempted.